1. Field
Example embodiments relate to hybrid matrix amplifiers and methods for calibrating the same.
2. Description of the Conventional Art
Conventionally, wireless transmitters at base stations and mobile stations include hybrid (or Butler) matrix amplifiers. Hybrid matrix amplifiers allow for signal paths to share the same amplifier resources, while meeting isolation requirements across output ports. Hybrid matrix amplifiers are generally well-known.
Prior to or during operation, hybrid matrix amplifiers must be calibrated to maintain output port isolation. Conventionally, a hybrid matrix amplifier is calibrated by periodically transmitting a training signal. But, transmission of training signals is undesirable because training signals are not compliant with regulatory (e.g., Federal Communications Commission (FCC), European Telecommunications Standards Institute (ETSI), 3rd Generation Partnership Project (3GPP), etc.) emissions designators.
Moreover, during transmission of training signals, normal traffic signals are interrupted, which may cause service outages.
Transmission of training signals also increases overall system interference levels in neighboring radio coverage areas, which may cause additional outages. Additional hardware and firmware is also required to generate the training signals.